The invention relates to a reactor refueling containment system, where refueling is accomplished without removing the reactor vessel primary pressure boundary. More specifically, a barrier plate is used to form a primary coolant boundary and a closure head carries the applied pressure load. The barrier plate has all required penetrations for fuel replacement, instrumentation, and poision injection systems with an elastomer seal for each penetration. These penetrations are for inserting and removing fuel rods, assemblies, control rods, etc. Because of the large number of penetrations required, it was thought that the most efficient closure head would be one that is removed for refueling (Heads-off refueling) as in current light water reactors. Such a closure head would require penetrations only for control rods and instrumentation.
The design of heavy water reactors have special requirements that make refueling as currently done in light water reactors inappropriate. Both Heavy and light water reactors require ready access to the reactor cores for fuel installation and refueling. In commercial light water reactors this is accomplished by depressurizing the system and removing the reactor vessel head to a storage area. During refueling, the area located above the reactor is flooded with additional light water to provide added nuclear shielding. This method is more commonly called "Heads-off" method of refueling. This allows the light water surface to be in direct contact with the air in the containment area.
While appropriate in light water applications this method is inadequate for refueling heavy water reactors. The tritium ladden heavy water causes two problems with the Heads-off method. First, the tritiated heavy water evaporates very quickly and contaiminates the containment area which is undesirable and hazardous. Secondly, there is a contamination of the heavy water reactor coolant from light water vapor and humidity in the containment environment. This contamination by the light water is an impairment to subsequent operation of the heavy water reactor and should be avoided. Thereby requiring that a barrier be provided between the heavy water coolant and containment environment.
The reactor refueling system of the instant invention eliminates the need for a seal plate mechanism and potential long term exposure of the heavy water to the atmosphere. Thereby, eliminating the need for massive environmental cleanups and their associated costs now required with the present Heads-off method.